A most natural magazine ebbs and flows like a king tide while articulating the obvious:
"Earth’s temperature has surged in the past two years, and climate
scientists will soon announce that it hit a milestone in 2024: rising to more than 1.5 °C above pre-industrial levels.
But is this sudden spike just a blip in the climate data, or an early
indicator that the planet is heating up at a faster pace than
researchers thought?"
"The question is not "is sea level rise accelerating?"
The consensus is that sea level rise (SLR) is accelerating.
The answer, then, is based on a three-fold spectrum: "how much was there
in the past?", "how much is there now?", and "how much will there be in
the future?"
Any historical or current data is ok to use to build upon, because we really need to use a known base from which to calculate prospective acceleration."
Fair enough, but I still just had to apply it to the states of the USA that contain tide gauge stations that have measured sea level at coastlines (PSMSL).
Regular readers of Dredd Blog know that we can read the history and herstory of sea level change, and its causes, written by the Warming Commentariat in those linked-to series posts above.
They tell a tale which is primarily that "thermal expansion causes most sea level rise" or "thermal expansion causes half of sea level rise".
More recently however it is more likely to be reported by different writers that "thermal expansion causes some sea level rise".
But, I have yet to read any Warming Commentariat papers that mention "thermal contraction".
Their "sticking point" for not considering that normal, every day sea level change event is "how in the world can adding heat to seawater cause thermal contraction"?
Let's consider that when the most normal of physics events caused by the Second Law of Thermodynamics takes place, that is, when hot flows spontaneously to cold, i.e. when 'warmer' flows to 'cooler' water molecules near it, the temperature at both locations change.
One location looses heat the other gains heat, so both thermal contraction and thermal expansion take place.
The formula is:
V = volume T = temperature β = thermal expansion coefficient
ΔV = V0 β ΔT or V1 = V0 * β * (T0 - T1)
(On Thermal Expansion & Thermal Contraction - 20). Before one exercises that formula they should remember that "V0" must be calculated using an unchanging mass of sea water over the period of time ("ΔT") being calculated:
"The misuse of the mass unit value is also a factor:
"A common practice in sea level research is to analyze separately the variability of the steric and mass components of sea level. However, there are conceptual and practical issues that have sometimes been misinterpreted, leading to erroneous and contradictory conclusions on regional sea level variability. The crucial point to be noted is that the steric component does not account for volume changes but does for volume changes per mass unit (i.e., density changes). This indicates that the steric component only represents actual volume changes when the mass of the considered water body remains constant."
(Journal of Geophysical Research: Oceans, emphasis added). There is a way to derive and use the appropriate mass unit value and keep it fixed while calculating its volume changes over time (thermal expansion and contraction is the changing of volume of a fixed mass unit of seawater over time caused by temperature changes of that fixed mass unit of seawater)."
(In Search Of Ocean Heat - 8). One can readily see that changes in temperature "ΔT" at the depth location of the fixed mass of seawater, which said temperature change is expressed as "(T0 - T1)", will render changes in volume ΔV into positive (thermal expansion) or negative (thermal contraction) values, depending on whether T1 is larger or smaller than T0.
In other words, the mass of seawater will have volume change (thermosteric sea level change) causing either sea level rise or sea level fall at that depth layer depending on changes in temperature at that depth layer.
The scientist or researcher utilizes measurements of seawater taken by a "thermometer" and a "depth recorder".
When commencing those thermal expansion and thermal contraction calculations the World Ocean Database is the best place to gather relevant data (WOD Update).
That source also has good base data (latitude & longitude based "Zones") with which to determine a depth layer mass (WOD Zones).
That source satisfies the in place, actual measurements (a.k.a. "in situ") requirements.
A further elaboration as to how the thermal calculations using those measurements came to be would bring up the Thermodynamic Equation of Seawater (TEOS-10).
III. What About β ?
The formula I am discussing has the symbol "β" which is the "thermal expansion coefficient":
"Dredd Blog uses the TEOS-10 toolkit's gsw_alpha function to calculate the thermal expansion coefficient:
"This site [teos-10.org] is the official source of information about the Thermodynamic Equation Of Seawater - 2010 (TEOS-10), and the way in which it should be used.
TEOS-10 is based on a Gibbs function formulation from which all thermodynamic properties of seawater (density, enthalpy, entropy sound speed, etc.) can be derived in a thermodynamically consistent manner. TEOS-10 was adopted by the Intergovernmental Oceanographic Commission at its 25th Assembly in June 2009 to replace EOS-80 as the official description of seawater and ice properties in marine science."
Of the gsw_alpha function, that official source says:
"Hence we may take the thermal expansion coefficient [a0] evaluated [from] gsw_alpha(SA,CT,p) as essentially reflecting the full accuracy of TEOS‐10."
The thermal expansion and contraction graphs (Appendix TsSlc) will be the most surprising to the Warming Commentariat, especially when compared to the actual sea level change in those states (The US States of Sea Level Change - 5).
If the Jupiter Watchers can present a more interesting view of Jupiter (Fig. 1), the Warming Commentariat should be able to do the same for causes of sea level change.
